Gas-producing charge



V 3,033,717 GAS-PRODUQIING CHARGE p11 F. Preckel, Cumberland, Md.,assignor to Hercules Powder Company, WilmingtomDeL, a corporation ofDelaware a No Drawing. Filed Apr. 14, 1955, Ser. No. 501,441

lfiClaims. (Cl. 149-100) This invention relates to the production ofsmokeless powders and more particularly to the production of smoke less.powders having peculiarly desirable ballistics for applications injet-actuated devices. It is well known that there is a definite anddirect relationship between the pressure at which a smokeless pow derpropellant burns and its burning rate. This, relationship may bemathematically expressed as r=cP or as log r=n log P+log c, where r isthe burning rate, P is the pressure at; which the. burning rate ismeasured, and c and n are constants characteristic of a givenpropellant. Thus, when-a plot of log r against log Pisl made for theconventional propellant,a straight line of slope n is ob tained showingan increase in burning rate for each inwhere AP is the experimentaldifierence in pressure under conditions of equilibrium burning due tothe temperature change Al; and? is the mean of the low temperature andhigh temperature pressures. I The advantage of having a low temperaturecoefficient of equilibrium pressure is obvious. If the coefficient islow, the jet-actuated device may be designed for an unusually low rangeof service pressure over the wide temperature range ordinarily specifiedfor such devices in field use. Since existing propellants generally havetemperature coefiicients of equilibrium pressure of about v 0.8%/ C. ormore, service pressure may change by crease in pressure. Such arelationship is not disadvan tageous in'theconventional gun propellantand in fact is used to advantage in progressivepowders where it ishighly desirable to generate increased pressures after the projectile orshot charge has begun to move along the barrel. However, thisrelationship presents a serious problem in formulation of propellantsfor jet-actuated devices since once the desired operating pressure isreached,

totally different considerations obtain.

It is highly desirable, once the operating pressure of a jet-actuateddevice is reached, that the pressure generated by the burning propellantbe maintained as nearly contant aspossible; Accordingly, if thisresultis to'be attained, theslope n of the line representingthe'pressureburning rate relationship of the particular propellant mustdesirably approach zero in the zone of useful rocket pressure. In theprior art rocket powders, in all of which the slope n has a value of 0.7or over, any fracturing or slivering of the propellant charge leads to apressure build-up because of an increase in linear burning rateresulting from the increase in pressure due to. the increase in burningsurface. The higher the n value of the particular powder, the higherwill be the pressure rise encountered. Therefore, the results of such afracturing or slivering vary from .a highly undesirable thrustfluctuation, with consequent aberration in ballistics, to actual failureof the jet device if, with a propellant of high 11 value, the pressurebuild-upj is excessive. Even unusual roughness of'the charge causesserious changes in burning pressure and burning rate in the presentlyavailable rocket propellants and have been found to build up to anaberration of 5% or more in ballistics. Consequently, with thepropellants now available, there is very little allowabletolerance inmanufacture of .charges and nozzles for jet devices. A propellant havinga very low 12 value within the .range of useful rocket pressures,however,

, is obtained by firing identical samples 'of propellant under identicalconditions except for changes in temperature and pressure.Thecoeflicient may beexpressed as 100% or more in going from the lowestexpected temperature to the highest expected temperature. It istherepropellants and thereby hold variation in service pressures due. totemperature change to a minimum. If the coeffieient could be loweredfrom 0.8%/ C. to 0.4%/ C. or .less, service pressure variation would bediminished by at least one-half.

;As a result of the advantages set forth above for a propellant having alow n value and a low temperature coeflicient' of equilibrium pressure,the combination of those two ballistic characteristics would allowadditionally for important economies in the inert weight of jet-actuateddevices. This is clearly seen if the equation is examined which relatesthe ratio between the mass of propellant (m) and the mass of the jetdevice without propellant (M), the gas velocity of the burningpropellant (V), and the highest theoretically obtainable velocity of thejet device (V as follows:

' m V,,,,,,= .303V log (1 pressures, to decrease M by 10% and increasethe amount of propellant to give the same total initial weight, V wouldbe increased by a factor of about 1.15. This would be a l5% improvement.

In my copending application Serial No. 492,802, filed 'March 7, 1955, ofwhich the present application is a conthese effects that the finishedcomposition be characterized by a heat of explosion of not more. than900 calories per gram. If the smokeless powder to which one of theseballistic modifiers is added is a single-base powder, it shouldpreferably comprise from -95% of nitrocellulose and from 5-15 ofnonvolatile, nonexplosive plas- Q ticizer. If the propellant used is amultiple-base formula, it should preferably comprise from 40-85% ofnitrocellulose, from 1035% of explosive liquid nitric ester and from530% of a substantially nonvolatile, nonexplosive plasticizer. Up to andincluding 10% of one or moreof the ballistic modifiers selected from thegroup consisting of lead and the inorganic and aliphatic compounds of r=2 lead may be employed without adversely affecting the ballistics ofthe gas-producing compositions of the invention. However, it ispreferred to employ only sufiicient of the additive to effect thedesired modification in ballistics. In most cases, it has been foundthat 2% of the 5 various additives based on the weight of the smokelesspowder employed is ample. While lead powder, lead oxide, and leadstearate are the preferred modifiers, a substantial effect has beenobtained from the incorporation of lead or any inorganic or aliphaticcompound of lead.

Gas-producing compositions characterized by a low 11 value and a lowtemperature coefficient of equilibrium pressure have proved greatlyadvantageous in jet and rocket applications. Actually, the onlydifficulty which has been encountered lies in the fact that eachspecific formulation of smokeless powder and ballistic modifier has beencharacterized by a specific burning rate at specific pressures and thatthe plateau area of low n value wherein a substantially constant burningrate and pressure are obtained is a peculiar characteristic of a givencomposition. Consequently, in order to obtain either a higher rate ofburning in a particular pressure region of low 11 value or to move theregion of low 11 value to a higher pressure range, it has been necessaryto design a specific charge formula. Such a procedure obviously requiresa considerable amount of experimentation in order to obtain the desiredballistics even though the desired increase in burning rate or shift inthe region of low It value may be small. 7

The object of the present invention, therefore, is a gas-producingcomposition which is characterized by a low n value.

Another object of the invention is a gas-producing composition which ischaracterized by both a low It value and by a low temperaturecoefiicient of equilibrium pressure.

A further object of the invention is such a gas-producing composition inwhich the burning rate is substantially increased in a region of low nvalue within the range of useful rocket pressures.

An additional object of the invention is a means by which the burningrate of a gas-producing composition (Ii consisting of lead, the oxidesof lead, the inorganic compounds of lead and the aliphatic compounds oflead, and an amount of finely-divided carbon not substantially exceedingthe amount of lead or compound of lead; said gas-producing compositionhaving a heat of explosion of not more than 900 calories per gram.

The burning rates in the plateau or low n value region in useful rocketpressure ranges of powders modified by incorporation of lead or leadcompounds have generally ranged from about 0.20 to 0.35 inch/sec. By theaddition to compositions thus modified of finely-divided carbon inamounts not substantially exceeding the amount of lead and/or leadcompound employed, it is possible to increase plateau burning rates inthe range of useful rocket pressure far above the plateau burning ratesof the same compositions to which no carbon has been added. It has beenfound that a preferred range of carbon addition exists for eachballistic modifier chosen from the group consisting of lead andcompounds of lead. Within this range, the plateau burning rate isstrongly dependent on the carbon concentration and at optimumconcentration, n values of between 0.0 and 0.2 are readily obtained. Infact, negative n values are often obtained. Furthermore, there is alsoan optimum carbon content which will give the maximum burning rateattainable while still retaining an acceptably low slope in the desiredpressure ranges. Carbon concentrations which achieve these preferred andoptimum conditions are naturally functions of each particular basicformula of gasproducing composition. Generally, carbon concentrations of1% or less and lead or lead compound concentrations of 5% or less arepreferred. In all cases, however, the amount of carbon must not exceedthe amount of lead and/or lead compound employed. The upper limit oflead and/or lead compound ballistic modifier is 10%. Lead stearate isthe preferred ballistic modifier.

While the finely-divided carbon may vary in particle size, the smallerparticle sizes are most effective. The greatest increase in plateauburning rate which has been obtained has been with a carbon black havingan average particle size of 0.01 or less micron.

Having generally described the invention, the following examples arepresented for purposes of illustration.

having a low n value and a low temperature coefficient ballisticsarelshown for gas'pmducmg of equilibrium pressure in the range of usefulrocket Posmons avmgt egenera formula pressure can be substantiallyincreased without inordinate- Nitrocellulose (12.6% N) 58.5 1yincreasing the 11 value. Nitroglycerin 27.5

Generally described, the present invention is a gas- Triacetin 7.5-10.0producing composition comprising a smokeless powder Ethyl centralite1.0- 4.0 having uniformly incorporated therein an amount not Leadstearate 1.0- 6.0 exceeding 10% of at least one material of the groupCarbon (Excello, 0.03 micron) 0.2- 1.0

Table I VARIATIONS IN BALLISTICS WITH CONCENTRATIONS 0F LEAD STEARA'IEAND CARBON BLACK Composition Interpolated burning rate Graphical 72Temp. Ex 000%.]? Heat of equ l exp.

0.13. PbStr. Pressure At; 25 C. At50 0. Pressure ri l. 12.6% NG TA EC(added) (uomi- (p.s.i.) (iu./see.) (in./sec.) interval 71 pre s i i re(08 lg) N nal) (p.s.i.) (percent/ 1 58.5 27.0 8.5 4.0 None 2.0 500 0.150.16 300- 570 0.58 0.5 703 1,000 0.19 0.22 570- 840 0.1a 1, 500 0. 25 0.28 840-2, 250 0. 2, 000 0. 31 0. 34 2, 2504, 000 1. 00 2,500 0. 37 0. 4a2 58.5 27.0 8.5 4.0 0. 35 2.0 500 0.23 0.25 sou-1,400 0.07 0.4 778 1,000 0. 37 0. 40 1, 400-3, 000 o. 17 1, 500 0. 47 0. 50 3, 000-4, 000 0.50 2,000 0.49 0.53 2,500 0.51 0.55 58.5 27.0 8.5 4.0 0.5 2.0 500 0.22 0.2a sou-1,500 0.71 0.4 772 1, 000 0. 30 0. as 1, 5004, 000 0. 21 1, 5000. 4s 0. 51 4, 000-4, 600 0. 52 2,000 0. 51 0.54 2,500 0. 53 0.57 4 58.527.0 8.5 4.0 0.75 2.0 500 0.21 0.24 $204,000 0. 01 0 7 762 1 000 0. 320. as 1, 0004, 000 0. as

Heat of Percent 2.0. (As indicated).

Temp. coeff. of equilibrium pressure (Percent/ C.)

istic modifiers selected from the the inorganic compounds of leadGraphical-n Pressure interyal (p.s.1.)

ite

ycerin Rate at Rate at (in/sec.) (in/sec.)

centage of various ball group consisting of lead, and the aliphaticcompounds of lead. The following basic formula was employed:

Nitro Triacetin Ethyl central Ballistic modifier 10 Carbon black(Excello, 0.03 micron) 0.0-0.5.

Table II Iuterpolated burning rate Pressure (p.s.i.)

ing varysic composition:

58.5 5 Nitrocellulose (12.6% N) 58.5.

Table III BALLISTIG EFFECTS OF FINELY DIVIDED CARBONS OF VARIOUSPARTICLE SIZE rin CARBON BLACK EFFECT ON BALLISTIOS OF SOME PLATEAUPROPELLANTS In Table II, ballistics are shown for gas-producingcompositions formed by adding 0.5% of carbon hav ing particle size tothe following ba Nitrocellulose (12.6% N) Nitroglyce Triacetin Ethylcentralite Lead stearate 1 Ball milled and screened thru a 325 meshscreen. 2 Passes thru a 325 mesh screen as supplied.

In Table III, the ballistic data are set forth to illustrate the effectof carbon black addition to gas-producing compositions of the inventioncontaining the indicated per- I m w 0 N 8 7 p a w fme nmm m M mfi s oGene m w e 8 007% mm H 1000 000 w .1 0000 500 0600 700 w. m) 3850 090 amm. 2 L2 r. 4 a new wwwm We 1385 30% 2 1'2 4 818538 B e izzaizfmm M0000000000 r 5 I r. g t.m m A r. C 6851769 8 u o C 1123329 A fiA M m 0000 0 0 0 0 0 0 e n M A0 1 m. e

000 000 H ooomooomww t S.J 50505-00505 55 i i 1 i i v i 1122 1122 .m mo.r\ n d 9 5 %6 n b d o 0 r3 3mm N C n n w n. n n n w r e u u m u u m n mm n m m m w 5 n d m a u n 1.. m 0 n 4 X E 4 5 8 3 ble II -Con nedInterpolated burning rate Graphical 1: Temp. Garbo V coefi. of- Heat ofEx. Lead compound (percent) black equilibrium exp.

(added) Pressure" At 0. At 50 0. Pressure pressure (eaL/g.) (p.s.i.)(in/sec.) (in/sec.) inter al 0 (percent/ (0.01.) J-) 36 4.0% leadmolybdate None 500 0. 21 0. 24 300.- 730v 0. 63 0. 7 897 1, 000 0. 340.48 640-2, 000. 0. 45 1, 500 0. 54 0.58 2000-3, 000 0.15 2, 000 0. 600. 64 3, 000-4, 000 0. 63 1 2, 500 .0. 64 0. 68 38"-.. 1.0% meta leadpaste None 500 0.22 0.24 300- 740 0.32 693 9 2, 500 0.40 0.44 39 do 0.2500 0. 23 l 0.24 200-1,250 0.76 685 1, 500 0. 47 0. 49 2, 900-4, 000 0.58 2,000 0.48 0. 51 2, 500 0.49 0. 52 2.0%1ead perchlorate None 500 0.25 '0. 28 300- 490 0. 55 873 l, 500 0. 41 0. 45 900-1, 375 -0. 17 0. 202, 000 0.47 0.53 1, 375-2, 350 0. 53 2,500 0.55 0.62 2, 350-4, 000 0.8142 4.0% lead 2-et11yl hexoate None 500. 0.10 0.19 100- 200 1.2 0.3 8281, 500 0. 52 0. 54 a, 100.4, 000 0. 50 2, 000 0.56 0.59 2,500 0. 0.6344..-" 2.0% lead methoxy p10pi0nete None 500 0.16 0.18 150- 350 0.50 8991, 000 0, 28 0.29 330- 800 0.42 1, 500 0. 31 0. 34 800-1, 325 0. 03 0.21 2.000 0.37 0.43 1 325-2, 025 0.63 2,500 0.45 0.52 2,025-4 .000 0.8946 2.0%lead ethoxy proplonate None 50 0.23 0.26 300- 530 0.91 887 1, 0000. 24 0. 28 530-1, 000 0. 00 0. 50 I, 500 0. 30 0. 34 1, 000-2, 0. 50 2,000 0. 35 0. 41 2, 100-4, 000 1. 20 2, 500 0. 44 0. 50 r 47 do 0. 4 5000. 22 0. 25 310-1, 0. 75 s23 1, 500 0.45 0. 47 1, 700-2, 300 0. 21 0.092, 000 0. 46 0. 45 2, 300-4, 000 0. 65 2, 500 0. 45 0. 51 48 2.0%tribasic lead maleete None 500 0.20 0.22 260 0.24 839 1, 000 0. 32 0. 34750-1, 350 0. 00 0. 36 1, 500 0. 35 0. 42 1, 350-4, 000 0. 70 2, 0000.44 0.50 2, 500. 0. 52 0.60 ,50. 1% lead NOIIG 500 0.22 0. 24 300- 7100.37 0.3 696 52 40% lead sulfide None 500 0. 24 0. 25 300- 530 0.32 0.3'890 1, 000 0. 28 0. 30 530-1, 200 0. 20 1, 500 0. 35 0. 38 1, 200-4, 0000. 82 2, 000 0. 44 0.49 2, 500 0. 53 0. 59 53 (10 0.5 500 0.38 0.43 300-550 0.66 0.4 869 .1 1, 000 0.54 0.59 550-1,775 0.44 1, 500 0. 65 0. 711, 775-4, 00 0. 19 2,000 0. 72 0.77 2,500 0.74 0.80 64 4% lead monoxideNone 500 0. 17 0.19 550 0.02 0. 4 834 1, 500 0. 32 0. 38 1, 450-4, 0000. 97 2, 000 0. 42 0. 50 r 2, 500 0. 53 0. 62 55 do 0.5 500 0.23 0.26100- 0. 60 0.5 863 1,000 0.31 0.34 190- 700 0.18 1, 500 0. 40 0. 45700-1, 350 0. 57 2, 000, 0. 50 V 0. 56 1, 350:4, 000 0. 75 2, 50 0 0. 000. 66 56, 1% tetraethyl lead None 500' 0.23 0.24 300- 500 0.24 0.3 682Table lIICont 1nued Interpoiated burning rate Graphical 11 Temp. Carboncoefi. of Heat of Ex. Lead compound (percent) black equilibrium exp.

(added) Pressure At 25 0. .41; 50 0. Pressure pressure (020.!)

(p.s.i.) (in./sec.) (in/sec.) interval n (percent/ (p.s.i.) O.)

1, 000 0. 30 0.34 2, 175-3, 000 0. 50 1, 500 0.34 0.38 2, 000 0.37 0.412,500 0.41 0.45 58.. 1.5% lead acetate None 100 0.064 0.073 100- 2600.15 0.7 609 200 0. 076 0.085 270-4, 000 0. 74 300 0.087 0.100 400 0.1070.122 500 0.127 0.141 60 1% lead ethoxy-aoetate None 500 0.16 0.19 300-380 0.24 0.7 820 1, 000 0. 0. 23 880-2, 150 0. 80 1, 500 0. 28 0. 32 2,150-4, 000 1. 38 2,000 0. 36 0.40 2,500 0.47 0.53 til 0. 3 500 0.22 0.25800-1, 250 0. 70 0. 2 807 1 Lead flakes, 80% through 325 mesh,/minera1spirits containing 10% stearie acid-90/10.

The examples in Table 'IV illustrate that it is undesirable to employmore than the necessary amount of finelydivided carbon and that plateauballistics are not obtained where the amount of carbon substantiallyexceeds the amount of lead or lead compound.

aliphatic compounds are generally operable in lowering the n value andthe temperature coefficient of equilibrium pressure in smokeless powdercompositions having a heat of explosion of not more than 900 caloriesper gram,

35 some of the specific compounds, and particularly lead Table IVBurning rate Graphical 11 Temp. 0. (in/sec.) coefi. of N0 Carbon Leadequilib- Heat 0! Ex. 12.6% N NG TA E0 black stearate rium exp.

(added) (nominal) 1,000 1,500 Pressure pressure (caL/g.)

p.s.l. p.s.i. interval at (percent/ (p.s.i.) C.)

58. 5 5 None 10 0. 19 0.26 200- 500 0 3 750 58. 5 26 5 1 10 39 44 1,000-3, 000 0.3 5 710 58. 5 26 10 10 39 49 1, 000-2, 500 6 7 435 58. 5 285. 5 8 None 1 22 26 660-1, 250 2 3 760 58. 5 27 8. 0 1 0.5 5 1 38 Noplateau 740 l Nitrodiphenylamine substituted for ethyl centralite.Norn.-NC =nitrocellu1ose, NG =nitrog1ycerin,

EXAMPLE 67 The following single base gas-producing compositions wereprepared: A. Nitrocellulose (12.6% N) 95.0 Ethyl centralite 1.0

Lead stearate 4.0 B. Same except for addition of 0.5% carbon black.

These compositions had the following comparative properties:

From the foregoing examples and from the disclosure of the copendingapplication, Serial No. 492,802, it is evident that while lead, itsinorganic compounds and its TA triacetin, E C =ethyl centrallte.

stearate, are more effective than others. In like manner, while theaddition of finely-divided carbon will raise the burning rate in theplateau region of all these compositions, some combinations of ballisticmodifier and carbon are more desirable than others. From the combinedviewpoints of effectiveness and economy, combinations of lead stearateand carbon are preferred.

From the examples it is further seen that relatively small amounts offinely-divided carbon will usually produce the desired burning rateincrease in the plateau region. In fact, optimum results are generallyencountered when the finely-divided carbon constitutes between 10 and33% by Weight of the lead and/ or lead. compound employed. Greateramounts of carbon may be employed up to 10% by weight of thegas-producing composition as long as the amount of carbon neversubstantially exceeds the amount of ballistics modifier. If the amountof carbon employed does exceed the amount of plataeauproducing agent,plataeau ballistics are detrimentally affected. Furthermore, increasingthe carbon content of a particular powder composition brings about acorresponding increase in brittleness in the powder. In addi- 13 tion itwill be appreciated that addition of unnecessary amounts of either theplateau-producing modifier or the carbon effects a cooling of the powderwhich lowers p l. and snitahil yfiaassque y. it is undesirable to employmore of either modifier than is necessary to obtain the desiredmodification in ballistics.

While the ranges given for the conventional components of the singleormultiple-base powders are not critical as long as the heat of explosionof the powder with the added modifier does not exceed 900 calories pergram, it has been found that powders prepared according to these rangesare more apt to come within this critical calorific requirement.

The compositions of the invention may be prepared by solventlessextrusion. In the conventional solventless process, water-wetnitrocellulose and the other ingredients are admixed in a Schrader bowlwith water. The resulting slurry or paste is dried to 10% water and iscolloided and dried between hot colloiding. rolls which may beeven-speed or differential-speed rolls as desired. The resultingcolloided, dry sheets are then cut into disks or convolutely rolled intocarpet rolls. The disks or carpet rolls are then extruded to desiredgrain size. Flake powder may be formed by suitably shredding the sheet.The resulting grains are normally glazed, usually with graphite, tolower static generation and to improve flowing characteristics.

The compositions of the invention may also, be made by the solventprocess. in the usual solvent process, the

water in hydrated nitrocellulose is first replaced, for exa Sigma blademixer. This dough is then formed into green grains, usually by extrusioninto cords and cutting the cords to the desired length. The green grainsare then subjected to solvent removal steps. The greater portion of thesolvent is normally removed by passing a warm inert gaseous medium suchas air or flue gas over the grains. The remainder of the solvent whichcan be practically removed is then usually leached out by a watertreatment. Water is. then removed by an air dry step and the dry grainsare normally given a glaze, usually of graphite, to lower staticgeneration and to improve flowing characteristics.

In the usual casting process, tiny singleor double-base powder grains,prepared by either the solvent orsolventless techniques, are introducedinto a mold together with suitable plasticizers. When the castings arecured, preferably by warm air storage at temperature of from about 100F.to about 160 F., the plasticizers cause the grains to coalesce into aunitary mass of plastic composition. Thev preferred casting process isthat disclosed in the copendingapplication of Gordon W. McCurdy, SerialNo.

28,218, filed May 20, 1948.

As is well known to the art, colloiding solvent can be removedfrompowder grains of large diameter and web onlywith extreme. difliculty.This difficnlty increases as the webthickness is increased. It istherefore desirable to prepare grains of the multiple-base formulationsof this invention by solventless extrusion or by a suitable castingprocess. It is preferredto extrude grains up to about or 6. inches indiameter and to cast all'larger grains. Casting of the larger grains ispreferred because the cost andmassive nature of extrusion presses largeenough to produce grains of over 5 or 6 inches in diameter becomeprohibitive.

The single-base formulations given in the examples are preferably madeby a conventional solvent process, extruded, and cut to the desiredgranulation. Such a process limits the possible size of the single-basegrains to a diameter or web thickness which will allow sufficientremoval of the colloiding solvent. Grains of solventcolloided powderhaving large diameter and web are, of course, operable and as long asthe heat of explosion does not exceed about 900 calories per gram,addition of the disclosed modifiers according to this invention willeffect the desired modification in ballistics. It is, of course, wellknown that the change in ballistics during storage caused by gradualmigration and evaporation of the colloiding solvent is the reason whylarge grains of solvent-colloided powder are not manufactured. Asimproved processes and means for solvent removal are developed, it willperhaps be possible to produce correspondingly larger grains ofsolvent-colloided powder which are ballistically stable. 7 i

t is not preferred to produce single-base grains by solventlessextrusion or by casting because, in order to keep the powder in thesingle-base category, the plasticizer employed to bring about colloidingand/or consolidation must be of lower potential than the nitrocellulose.The necessary amount of plasticizer, therefore, so lowers the potentialthat such powders have only a limited application. Nevertheless,incorporation of the disclosed modifiers in single-base grains preparedby solventless extrusion or by casting still results in a low 11 valueand a low temperature coefficient of equilibrium pressure.

If the gas-producing charges of this invention are made by solventlessextrusion, the ballistic modifier or modifiers are preferably added atsome time prior to dehydration of the water slurry and the additivesystem is mixed to a state of homogeneity. The slurrry is thendehydrate, the moist mass is rolled into colloided sheets, the sheetsare male into rolls and the rolls are extruded in the conventionalmanner. However, it is often found advantageous to add the ballisticmodifiers during the rolling operation, rather than to the water slurry.If the Well known Schrader process is employed, the modifiers may beadded to the hydrated nitrocellulose in the mixing bowl in any preferredorder. A portion of the water is evaporated prior to rolling. TheSchrader process is preferred when water-soluble plasticizers areemployed.

If the charges of this invention are prepared by solvent extrusion, theballistic modifier or modifiers are preferably added to the dehydratednitrocellulose after it has been broken up in a mixelz The modifiers maybe introduced with the plasticizer or plasticizers or may be addedbefore or after introduction of the plasticizer as may be desired in theparticular formulation.

If the grains are made by casting, the ballistic molifier ishomogeneously incorporated during'the preparation of the casting powder.

The heat of explosionof an explosive composition may be experimentallydetermined in the known manner by actually exploding a sample of thesubstance in a bomb calorimeter under conditions which insure completecombustion of the constituents of the composition, and measuring theheat liberated. However, in the case'of smokeless powder compositions,which contain at most only small portions of inorganic material, it isusually desirable to determine the heat of explosion by calculation.Thecalculation of heats of explosion is especially desirable in order toaccurately predetermine the calorific value of a proposed compositionprior to its formulation. In this calculation, use is made of a simplerelation; namely, the heat of explosion per gram of powder is equivalentto the sum of the products of the weight fraction of a 'givenconstituent by the contribution to the heat of explosion of theconstituent, This contribution of the constituent is for conveniencetermed the partial calorific potential or the partial heat of explosion,and is usually designated as K Thus, th heat of explosion of thecomposition is derived by the equation:

Heat of explosion=zX K where X, is the weight fraction of the powdercomponent i.

For compositions consisting principally of carbon, hy-

1 drogen, oxygen, and nitrogen, K is quickly and accurately determinedaccording to the following equations:

where 0 is the number of gram-atoms of oxygen per gram of the powdercomponent i, C is the number of gram-atoms of carbon per gram of thepowder component i, H is the number of gram-atoms of hydrogen per gramof the powder component i, H0. is the heat of combustion at 25 C. andconstant volume, and AEf is the heat of formation per gram of the powdercomponent i from its elements.

Partial heats of explosion for inorganic substances such as theballistic modifiers of the invention are not quite as readily calculatedbut may, nevertheless, be determined according to methods disclosed byDe Pauw in Z. f. ges. Schiessund Sprengstoffwesen, 32, 11, 36-, 60(1937); or by Hirschfelder and Sherman in Simple Calculation ofThermochemical Properties for Use in Ballistics, O.S.R.D. Report No.1300, declassified and issued as PB27421S.

Actually, it is unnecessary to experimentally determine the K values forthe various constituents of the smokeless powders in accordance with theinvention since tables of the partial heats of explosion for thesematerials are available as published data. The following is a listing ofthe K values of the normally usel smokeless powder components and manyof the operable ballistic modifiers in accordance with the invention.

Substance (i): Partial heat of explosion (cal./ g.)

Acetone 1938 Carbon black 3330 Diamylphthalate -2190 Dibutylphthalate-2055 Diethanol nitramine dinitrate 1294 Diethylene glycol dinitrate1030 Diethylphthalate -1746 Dinitrotoluene 140 Diphenylamine 2684Diphenylurea -2227 Diphenylurethane -2739 Ethyl alcohol 1749 Ethylcentralite 2398 Ethyl urethane 1639 Graphite -3377 Lead 0 Lead acetate(trihydrate) 282 Lead azide 385 Lead bromide -137 Lead carbonate (basic)471 Lead chloride 151 Lead perchlorate 1250 Lead chromate 977 Leaddiacetylacetonate 868 Lead ethoxyacetate 639 Leal Z-ethyl hexoate 1336Lead fluoride -127 Lead hydroxide -189 Lead iodide 91 Lead linoleate1982 Lead maleate (tribasic) -320 Lead molybdate 403 Lead naphthenate-2048 Lead oleate 20l0 Lead oxalate 58 Lead oxide (PbO) 67 Lead oxide(Pb O 139 Lead oxide (PbO 302 Lead methoxy propionate 634 Lead ethoxypropionate 1400 Lead stearate Substance (i): Partial heat of explosion(cal./ g.) Lead sulfate -l50 Lead sulfide 222 Lead tartrate 172 Leadtetraethyl l231 Nitrocellulose 13.25% N 1041 13.15% N 1027 13.00% N 100712.60% N 951 12.20% N 895 12.00% N 867 11.50% N 797 Nitroglycerin 1785Nitroguanidine 720 Triacetin 1284 Water -5 In order to produce theplateau" type ballistics of the invention, the modifiers must beuniformly incorporated with the other ingredients of the composition;that is, the modifier must be intimately admixed with the otheringredients within each particle of the composition whether the chargeis a loose charge of individual grains or consists of a single grain ofany desired size. The glazing or coating of a single grain or aplurality of grains in a loose charge will not produce the desiredmodification in the pressure-burning rate relationships. Thus, powdergrains coated or glazed with a lead compound to render them free-flowingare not operable in the invention.

The advantages of the gas-producing compositions of this invention overpresently available formulations are readily apparent. T he compositionsof this invention are characterized by distinguishing properties whichhave heretofore been found highly desirable but unobtainable; namely, alower temperature coefficient of equilibrium pressure and a constant ormore nearly constant burning rate over a wide pressure range within thezone of useful rocket pressures. Furthermore, by varying the carbonconcentration in the gas-producing compositions of the invention withinthe prescribed limits, the burning rate of the plateau region, or regionof low n value, may be greatly increased without shifting the plateauout of the zone of useful rocket pressures.

What I claim and desire to protect by Letters Patent is:

1. A gas-producing composition consisting essentially of a smokelesspowder having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% of atleast one material selected from the group consisting of lead, theinorganic compounds of lead and the aliphatic compounds of lead, and anamount of finely-divided carbon not substantially exceeding the amountof the said material, said gas-producing composition having a heat ofexplosion not exceeding 900 calories per gram and having a value of lessthan 0.7 for the slope n of the line representing the pressure-burningrate relationship.

2. A gas-producing composition consisting essentially of a smokelesspowder having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% oflead and an amount of finely-divided carbon not substantially exceedingthe amount of lead, said gas-producing composition having a heat orexplosion not exceeding 900 calories per gram and having a value of lessthan 0.7 for the slope n of the line representing the pressureburningrate relationship.

3. A gas-producing composition consisting essentially of a smokelesspowder having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% oflead oxide and an amount of finely-divided carbon not substantiallyexceeding the amount of lead oxide, said gasproducing composition havinga heat of explosion not exceeding 900 calories per gram and having avalue of 17 less than 0.7 for the .slope n of the line representing thepressure-burning rate relationship.

4. A gas-producing composition consisting essentially of a smoleklesspowder having uniformly incorporated therein and intimately admixedtherewith within-each particle thereof an amount not exceeding of leadZ-ethylhexoate and an amount of finely-divided carbon not substantiallyexceeding the amountof lead Z-ethylhexoate, said gas-producingcomposition having a heat of explosion not exceeding 900-calories pergram and having a value of less than 0.7 for the slope n of the linerepresenting the pressure-burning rate relationship,

5. A gas-producing composition'consisting essentially of a smokelesspowder having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% of afatty acid, salt of lead and an amount of finely-divided carbon notsubstantially exceeding the amount of fatty acid salt of lead, saidgas-producing composition having a heat of explosion not exceeding 900calories per gram and having a value of less than 0.7 for the slope n ofthe line representing the pressure-burning rate relationship.

6. A gas-producing composition consisting essentially of a smokelesspowder having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount notexceeding 10% oflead stearate and an amount of finely-divided carbon not substantiallyexceeding the amount of lead stearate, said gasproducing compositionhaving a heat of explosion not exceeding 900 calories per gram andhaving a value of less than 0.7 for the slope n of the line representingthe pressure-burning rate relationship.

7. A gas-producing composition consisting essentially of a smokelesspowder containing from 85 to 95% nitrocellulose and having uniformlyincorporated therein and intimately admixed therewith within eachparticle thereof an amount not exceeding 10% of at least one materialselected from the group consisting of lead, the inorganic compounds oflead and the aliphatic compounds of lead, and an amount offinely-divided carbon not substantially exceeding the amount of the saidmaiierial, said gasproducing composition having a heat of explosion notexceeding 900 calories per gram and having a value of less than 0.7 forthe slope n of the line representing the pressure-burning raterelationship. I

8. A gas-producing composition consisting essentially of a smokelesspowder containing from 85 to 95 nitrocellulose and having uniformlyincorporated therein and intimately admixed therewith within eachparticle thereof an amount not exceeding 10% of lead and an -amount offinely-divided carbon not substantially exceeding the of a smokelesspowder containing from 85 to 95% nitrocellulose and having uniformlyincorporated therein and intimately admixed therewith within eachparticle thereof an amount not exceeding 10% of lead oxide and an amountof finely-divided carbonnot substantially exceeding the'amount of leadoxide, said gasproducing composition having aheat of explosion notexceeding 900 calories per gram and having a value of less than 0.7 forthe slope n of the line representing the pressureburning raterelationship.

'10. A gas-producing composition consisting essentially of a smokelesspowder containing from 85 to 95 nitrocellulose and having uniformlyincorporated therein and intimately admixed therewith each particlethereof an amount not exceeding 10% of lead 2-ethylhexoate and an amountof finely-divided carbon not substantially exceeding the amount of leadZ-ethylhexoate, said gas-producing composition having a heat ofexplosion not exceeding 900 calories per gram and having a value of lessthan 0.7 for the slope n of the line representing the pressure-burningrate relationship.

11. A gas-producing composition consisting essentially of asmokelesspowder containing from 85 to 95% nitrocellulose and havinguniformly incorporated therein and intimately admixed therewith withineach particle thereof an amount not exceeding 10% of a fatty acid saltof lead and an amount of finely-divided carbon not substantiallyexceeding the amount of fatty acid salt of lead, said gasproducingcomposition having a heat of explosion not exceeding 900 calories pergram and having a value of less than 0.7 for the slope n of the linerepresenting the pressure-burning rate relations hip. Y

12. A gas-producing composition consisting essentially of a smokelesspowder containing from 85 to 95 nitrocellulose and having uniformlyincorporatedtherein and intimately admixed therewith within eachparticle thereof an amount not exceeding 10% of lead stearate and anamount of finely-divided carbon not substantially exceed-.

ing the amount of lead stearate, said gas-producing composition having aheat of explosion not exceeding 900 calories per gram and having a valueof less than 0.7 for the slope n of the line representing thepressure-burning rate relationship.

13. A gas-producing composition consisting essentially of a smokelesspowder containing nitrocellulose and at least one explosive nitric esterand having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% of atleast one material selected from the group consisting of lead, theinorganic compounds of lead and the aliphatic compounds of lead, and anamount of finely-divided carbon not substantially exceeding the amountof the said material, said gas-producing composition having a heat ofexplosion not exceeding 900 calories per gram and having a value of lessthan 0.7 for the slope n of the line representing the pressure-burningrate relationship.

14. A gas-producing composition consisting essentially of a smokelesspowder containing nitrocellulose and at least. one explosive nitricester and having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% oflead and an amount of finely-divided carbon not substantially exceedingthe amount of lead, said gasproducing composition having a heat ofexplosion not exceeding 900 calories per gram and having a value of lessthan 0.7 for the slope n of the line representing the pressure-burningrate relationship.

15. A gas-producing composition consisting essentially of a smokelesspowder containing nitrocellulose and at least one explosive nitric esterand having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% oflead oxide and an amount of finely-divided carbon not substantiallyexceeding the amount of lead oxide, said gas-producing compositionhaving a heat of explosion not exceeding 900 calories per gram andhaving a value of less than 0.7 for the slope n of the line representingthe pressure-burning rate relationship.

16. A gas-producing composition consisting essentially of a smokelesspowder containing nitrocellulose and at least one explosive nitric esterand having uniformly incorporated therein and tintimlately admixedtherewith within each particle thereof an amount not exceeding 10% oflead 2-ethylhexoate and an amount of finelydivided carbon notsubstantially exceeding the amount of lead Z-ethylhexoate, saidgas-producing composition having a heat of explosion not exceeding 900calories per gram and having a value of less than 0.7 for the slope n ofthe line representing the pressure-burning rate relationship. v

17. A gas-producing composition consisting essentially of a' smokelesspowder containing nitrocellulose and at least one explosive nitric esterand having uniformly incorporated therein and intimately admixedtherewith of fatty acid salt of lead, said gas-producing compositionhaving a heat of explosion not exceeding 900 calories per gram andhaving a value of less than 0.7 for the slope n of the line representingthe pressure-burning rate relationship.

18. A gas-producing composition consisting essentially of a smokelesspowder containing nitrocellulose and at least one explosive nitric esterand having uniformly incorporated therein and intimately admixedtherewith within each particle thereof an amount not exceeding 10% oflead stearate and an amount of finely-divided carbon not substantiallyexceeding the amount of lead stearate, said gas-producing compositionhaving a heat of explosion not exceeding 900 calories per gram andhaving a value of less than 0.7 for the slope n of the line representingthe pressure-burning rate relationship.

References Cited in the file of this patent UNITED STATES PATENTS1,357,865 Henning Nov. 2, 1920 2,385,135 Holmes Sept. 18, 1945 2,498,388Ball Feb. 21, 1950 2,982,638 Cooley May 2, 1961 v FOREIGN PATENTS621,685 Great Britain Apr. 14, 1949

1. A GAS-PRODUCING COMPOSITION CONSISTING ESSENTIALLY OF A SMOKELESSPOWDER HAVING UNIFORMLY INCORPORATED THEREIN AND INTIMATELY ADMIXEDTHEREWITH WITHIN EACH PARTICLE THEREOF AN AMOUNT NOT EXCEDDING 10% OF ATLEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF LEAD, THEINORGANIC COMPOUNDS OF LEAD AND THE ALIPHATIC COMPOUNDS OF LEAD, AND ANAMOUNT OF FINELY-DIVIDED CARBON NOT SUBSTANTIALLY EXCEEDING THE AMOUNTOF THE SAID MATERIAL, SAID GAS-PRODUCING COMPOSITION HAVING A HEAT OFEXPLOSION NOT EXCEEDING 900 CALORIES PER GRAM AND HAVING A VALUE OF LESSTHAN 0.7 FOR THE SLOPE N OF THE REPRESENTING THE PRESSURE-BURNING RATERELATIONSHIP.